Re: integer*8 speed vs integer*4 speed

On Feb 26, 8:16 pm, "Lynn McGuire" <nos...@xxxxxxxxxx> wrote:
Does anyone know of the relative speed difference of generally
using integer*8 over integer*4 ? Specifically in Win32.

It depends. The "standard" IA-32 instruction set doesn't have
instructions for 64-bit integers. A compiler which supports INTEGER*8
can do add and subtract in two instructions, but multiply and divide
may take many more and might be done in a routine call. A lot of other
operations that could be done in an instruction will also be done with
calls.

IA-32 has few registers available, so an I*8 probably gets moved in
and out of memory more than I*4. Use of SSE instructions can help with
this. There is of course the fact that you're using twice as much
memory, so if you're moving a lot of data you're doubling the load.

A lot will also depend on the particular compiler you use and the
instruction set you allow it.

If you have an application that is heavily into I*8 you'd be better
off switching to Win64.

Steve

.

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